html,body{
    height: 99%;
    width: 100%;
    padding-right: 1px;
    position: relative;
}

.back{
    height: 100%;
    width: 100%;
    position: relative;
}
.welcome{
    width:500px;
    height:100px;
    margin-left: 100px;
    margin-top: 30px;
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
}
.welcome h2{
    size: 20px;
}
.infoSwitch{
    width:500px;
    height:100px;
    margin-left: 100px;
    margin-top: 130px;
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
}